Corrosion of SS-304 in Vinyl Chloride service with Moisture 1

[rtsd]

We have SS-304 pipeline to handle the recovery of Vinyl Chloride from PVC reactor, it has moisture causing HCL, there is no problem with SS-304 pipeline but Ball Valve of SS-304 installed on this line having corrosion.

Kindly guide how to overcome this problem either by material upgradation or by changing valve type from Ball to Plug or other.

 

[MortenA]

You dont mention the type of corrosion that you encouter - is it indeed chloride stress corrosion or? For those of us not familiar with the process, is it a liquid (with water)? Is your pipe a material 304 or is it 304L?

Best regards

Morten

 

[rtsd]

yes Vinyl Chloride is in liquide form and the there is uniform corrosion of ball and seat of ball valve of SS-304/304L.
Pitting corrosion is the type of corrosion.

 

[MortenA]

SS are suseptible to pitting corrosion when in precense of chlorides. The solution seems to go for more molybdenum - but all SS can experience pitting. The fact that its the valve and not in the pipeline lead me to suspect that the pipeline has a good protective film whereas the valve dosnt. Theres nothing that can be done about that as such. A valve with a protective coating on the surfaces as well as another valve type may be a solution? Here you should take to the valve vendor.

Best regards Morten

 

[EdStainless]

Is it only the ball that is corroding?
If so try to look for a replacement set of valve trim with a ceramic ball.
I would stay with a ball valve, unless you can't find the trim in which case a plug valve might be a good option.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube